Attic insulation

Inspecting an attic, I observed brown spots on top of the white attic insulation. These spots appeared to be throughout the entire attic below the corroded roofing nails protruding through the sheathing. The home was vented with ridge and soffit vents. Built in 2005. No indication of any mold issues. Anyone see this before? Condensation problem possibly? The ridge vents did have baffles.

It does sound like condensation…The nails, sticking through were rusted/corroded. Do you have some pics of the underside of the roof sheathing? Did the ridge vent have a baffle? Were the eave vents blocked, at all?

I agree.
I have seen this frequently just like this nails rusted
Usual cause is Plumbing vent into attic or bath exhaust into attic

Pictures of corroded nails.

Inadequate attic ventilation.

Where the soffit vents blocked by insulation? This is a occasional problem I find here in AZ. If vent baffles are not installed it is easy for the insulation sprayer to get carried away